Theoretically, yes a NO2 supp would lower your BP. But how much vasodilation do OTC products actually cause? Very little.

But at 140/85 I wouldn't worry too much. Your BP isn't textbook perfect but that really isn't high either. Doctors tend to like to help the drug companies make some money, don't let him trick you into getting meds for it either. At your age I'm sure you really don't need it.

Best advice, maybe jog or ride a bike a little more. Drink more water.